librenms-librenms/includes/discovery/sensors/charge/linux.inc.php

<?php

if (preg_match("/(Linux).+(ntc)/", $device['sysDescr'])) {
    $sensor_type = "chip_battery_charge";
    $oid = '.1.3.6.1.4.1.8072.1.3.2.4.1.2.10.112.111.119.101.114.45.115.116.97.';
    $lowlimit     = 5;
    $lowwarnlimit = 9;
    $warnlimit    = null;
    $limit        = null;
    $descr = 'Battery charge';
    $index = '116.8';
    $value = snmp_get($device, $oid.$index, '-Oqv');
    if (is_numeric($value)) {
        discover_sensor($valid['sensor'], 'charge', $device, $oid.$index, $index, $sensor_type, $descr, 1, 1, $lowlimit, $lowwarnlimit, $warnlimit, $limit, $value);
    }
}

$oids = '.1.3.6.1.4.1.8072.1.3.2.4.1.2.7.117.112.115.45.110.117.116.1';
$value = snmp_get($device, $oids, '-Osqnv');

if (!empty($value)) {
    $type = 'ups-nut';
    $index = 1;
    $limit = 100;
    $lowlimit = 0;
    $lowwarnlimit = 10;
    $descr = 'Battery Charge';
    if (is_numeric($value)) {
        discover_sensor($valid['sensor'], 'charge', $device, $oids, $index, $type, $descr, 1, 1, $lowlimit, $lowwarnlimit, null, $limit, $value);
    }
}
unset($oids);